The invention relates to novel isocyanates containing tertiary amino groups, a process for preparing them, and also their use for the synthesis and modification of polymers.
The invention provides isocyanates of the formula (I) 
where
R1 and R2 are, independently of one another, alkyl having from 1 to 6 carbon atoms, where R1 and R2 may be joined to form a ring,
Z is alkylene having from 2 to 6 carbon atoms,
n is an integer from 0 to 20,
Y is alkylene having from 2 to 6 carbon atoms.
The alkyl radicals R1 and R2 may be linear or branched or joined to form an aliphatic ring, preferably a 5-membered or 6-membered ring. Preference is given to alkyl radicals having from 1 to 4 carbon atoms, and particular preference is given to methyl.
The alkylene radical Z preferably contains from 2 to 4 carbon atoms, particularly preferably 2 carbon atoms. n is preferably from 0 to 10, particularly preferably from 1 to 6.
Preference is given to isocyanates of the formula (II) 
where n=0 to 20, preferably from 0 to 10, particularly preferably from 1 to 6.
Examples of isocyanates according to the invention are the following compounds:
The present invention further provides a process for preparing isocyanates of the formula (1), which is characterized in that silyl compounds of the formula (III) 
are reacted with isocyanatocarboxylic chlorides of the formula (IV), 
where R1 , R2, Z, n, and Y are as defined above.
Silyl compounds of the formula (III) can be obtained by silylation of the corresponding hydroxyl compounds. Suitable hydroxyl compounds are, for example, 2-dimethylaminoethanol, 2-diethylaminoethanol, 2-dioctylaminoethanol, 3-dimethyl-aminopropanol, 3-diethylaminopropanol, 3-dibutylaminopropanol, 4-dimethylamino-butanol, 4-diethylaminobutanol, 5-dimethylaminopentanol, 6-dimethylaminohexanol, N-(2-hydroxyethyl)pyrrolidine, N-(2-hydroxyethyl)piperidine, N-(3-hydroxypropyl)-piperidine, N-(2-hydroxyethyl)hexamethylenmine, and also their ethoxylation products. Trimethylchlorosilane is a useful silylating agent for the purposes of the invention. Also useful are mixtures of trimethylchlorosilane and hexamethyl-disilazane. The parent hydroxy compounds in which n=1 to 20 can be obtained in a manner known per se by ethoxylation. It has been found that the use of strong acid ion exchangers is very useful for the isolation and purification of the ethoxylation products.
Isocyanatocarboxylic chlorides of the formula (IV) are known and can be prepared, for example, by reaction of aminocarboxylic acids with phosgene. Further details of the synthesis are described in W. Mormann, S. Hoffmann, W. Hoffmann, Chemische Berichte 120, 285-290 (1987) and in DE-A 2 120 090.
The reaction of the silyl compound of the formula (III) with the isocyanatocarboxylic chloride of the formula (IV) can be carried out in bulk without solvent. The reaction is exothermic and is preferably commenced at a low temperature of, for example, from 0xc2x0 to 30xc2x0 C. To control the exothermic reaction, it is advantageous for one of the reaction components, preferably the isocyanatocarboxylic chloride, to be added over a period of from 10 to 100 minutes. After the addition is complete, the reaction temperature is increased, for example to from 80 to 150xc2x0 C. To remove the trimethyl-chlorosilane formed, a slight vacuum of from 50 to 500 mbar can be employed. The conversion can be monitored by quantitative determination of the trimethylsilyl chloride liberated.
The isocyanates of the invention can be reacted with hydroxy and amino compounds (NH2 or NH) to form urethanes or ureas. The use of a catalyst is generally not necessary. However, known catalysts such as dibutyltin laurate, triphenylstibine or triphenylphosphine can be used if desired. The catalysts are then used in amounts of from 50 to 5000 ppm, based on the starting materials.
The isocyanates of the invention are particularly useful for carrying out polymer-analogous reactions. Thus, tert-amino groups can be introduced in a simple manner into existing polymers containing OH or NH2 groups. Particulate, crosslinked or uncrosslinked polymers, for example bead polymers, can also be reacted or modified with the isocyanates of the invention. The modification of magnetic, in particular superparamagnetic, bead polymers is also possible. In the reaction with crosslinked bead polymer, a swelling agent such as chloroform, methylene chloride or methyl ethyl ketone is employed to achieve high conversions.
Bead polymers which have been modified by means of the isocyanates of the invention can be used for numerous applications. Examples which may be mentioned are use as ion exchangers, as static phase in chromatography or for the isolation of nucleic acids in diagnostics.